0600-6-mt

If the temperature of atmosphere increases at constant absolute humidity, the percentage saturation would

- decrease
- remain constant
- increase
- none of these

0600-7-mt

If the temperature of atmosphere increases at constant absolute humidity, the wet-bulb temperature would

- decrease
- remain constant
- increase
- none of these

1988-5-b-vi-mt

Air with a dry bulb temperature \(t_{d1}\) and a wet bulb temperature \(t_{w1}\) is passed through a heater and then through an adiabatic cooler from which it emerges with dry and wet bulb temperatures of \(t_{d2}\) and \(t_{w2}\) respectively. Then

- always \(t_{w1} > t_{w2} \mbox { and } t_{d1} > t_{d2}\)
- always \(t_{w1} < t_{w2} \mbox { and } t_{d1} > t_{d2}\)
- always \(t_{w1} > t_{w2} \mbox { and } t_{d1} < t_{d2}\)
- \(t_{w1} < t_{w2} \mbox { and } t_{d1} \mbox { can be greater than, equal to or less than } t_{d2}\)

1990-5-v-mt

Lewis number = 1 signifies:

- \(\text {Pr} = \text {Sc}\)
- \(\text {Pr} = \text {Re}\)
- \(\text {Sc} = \text {Re}\)
- \(\text {Nu} = \text {Sh}\)

1998-2-13-mt

For the Air-Water system under ambient conditions, the adiabatic saturation temperature and the wet-bulb temperature are nearly equal, because

- water has a high latent heat of evaporation
- Lewis number is close to unity
- they are always equal under all circumstances
- solubility of the components of air in water is very small

1998-2-8-mt

Air, initially at 101.3 kPa and 40\(^\circ \)C, and with a relative humidity of 50%, is cooled at constant pressure to 30\(^\circ \)C. The cooled air has

- A higher dew point
- A higher absolute (specific) humidity
- A higher relative humidity
- A higher wet bulb temperature

2001-1-13-mt

The Lewis relation for air-water humidification is given by (\(k_Y\): mass transfer coefficient of moisture in air; \(h_G\): heat transfer coefficient; \(C_S\): heat capacity of vapor-gas mixture)

- \(\displaystyle \frac {h_G^2}{k_YC_S} = 1\)
- \(\displaystyle \frac {k_YC_S^2}{h_G} = 1\)
- \(\displaystyle \frac {h_G}{k_YC_S} = 1\)
- \(\displaystyle \frac {k_Y^2h_G}{C_S} = 1\)

2003-67-mt

The following plot gives the saturated humidity (\(H_e\)) versus Temperature (\(T\)).

Line joining \((H_1,T_1)\) and \((H_2,T_2)\) is the constant enthalpy line. Choose the correct one.

- \(T_1\) - Dew point Temp; \(T_2\) - Dry bulb Temp; \(T_3\) - Wet bulp Temp.
- \(T_1\) - Dew point Temp; \(T_2\) - Wet bulb Temp; \(T_3\) - Wet bulp Temp.
- \(T_1\) - Wet bulb Temp; \(T_2\) - Dry bulb Temp; \(T_3\) - Dew point Temp.
- \(T_1\) - Dry bulb Temp; \(T_2\) - Wet bulb Temp; \(T_3\) - Dew point Temp.

2016-13-mt

For what value of Lewis number, the wet-bulb temperature and adiabatic saturation temperature are nearly equal?

- 0.33
- 0.5
- 1
- 2

MN-2013-41-mt

Four psychrometric processes \(P\), \(Q\), \(R\) and \(S\) are shown in the psychrometric chart below.

These processes respectively represent

- dehumidification, humidification, sensible heating, sensible cooling
- sensible heating, humidification, dehumidification, sensible cooling
- dehumidification, sensible heating, sensible cooling, humidification
- humidification, sensible heating, dehumidification, sensible cooling

XE-2008-G-8-mt

If the moist air is heated at a constant pressure

- the specific humidity changes
- the relative humidity does not change
- the relative humidity decreases
- the relative humidity increases

XE-2009-E-2-mt

During the adiabatic saturation process

- the relative humidity increases but the specific humidity remains constant
- both the relative humidity and the specific humidity remain constant
- both the relative humidity and the specific humidity increase
- the relative humidity decreases but the specific humidity increases

1994-3-c-mt

If an insoluble gas is passed through a volatile liquid placed in a perfectly insulated container, the temperature of the liquid will increase. (True/False)

- True
- False

1989-5-ii-e-f-mt

Air is passed through a heater at constant pressure. The inlet and outlet conditions of the air are as follows:

Inlet:

Dry bulb temperature = 31.7\(^\circ \)C

Wet bulb temperature = 23.9\(^\circ \)C

Humidity = 30%

Outlet:

Dry bulb temperature = 70\(^\circ \)C

(i) The inlet air will have a dew point

{#1}

(ii) In the above problem, the air from the heater will have a humidity:

{#2}

2004-21-22-mt

An air-water vapor mixture has a dry bulb temperature of 60^{o}C and a dew point temperature of 40^{o}C. The total pressure is 101.3 kPa and the vapor pressures of water at 40^{o}C and 60^{o}C are 7.30 kPa and 19.91 kPa,
respectively.

(i) The humidity of air sample expressed as kg of water vapor/kg of dry air is

{#1}

(ii) The wet bulb temperature \(T_w\) for the above mixture would be

{#2}

1996-2-17-mt

In a mixture of benzene vapor and nitrogen gas at a total pressure of 900 mm Hg, if the absolute humidity of benzene is 0.2 kg benzene/ kg nitrogen, the partial pressure of benzene in mm Hg is

- 180
- 60.3
- 720
- 200

1999-2-11-mt

If the specific heats of a gas and vapor are 0.2 kJ/kg.K and 1.5 kJ/kg.K respectively, and the humidity is 0.01, the humid heat in kJ/kg.K is

- 0.31
- 0.107
- 0.017
- 0.215

2007-29-mt

If the percent humidity of air (30^{o}C, total pressure 100 kPa) is 24% and the saturation pressure of water vapor at that temperature is 4 kPa, the percent relative humidity and the absolute humidity of air are

- \(25.2, 0.0062\)
- \(25, 0.0035\)
- \(20.7, 0.0055\)
- \(18.2, 0.0035\)

2010-38-mt

At 25^{o}C and 90% relative humidity, water evaporates from the surface of a lake at the rate of 1.0 kg/(m^{2}.h). The relative humidity that will lead to an evaporation rate of 3.0 kg/(m^{2}.h), with other conditions remaining
the same, is

- 30%
- 50%
- 60%
- 70%

ME-2008-53-mt

Moist air at a pressure of 100 kPa is compressed to 500 kPa and then cooled to 35^{o}C in an aftercooler. The air at the entry to the aftercooler is unsaturated and becomes just saturated at the exit of the aftercooler. The saturation pressure
of water at 35^{o}C is 5.628 kPa. The partial pressure of water vapor (in kPa) in the moist air entering the compressor is closest to

- 0.57
- 1.13
- 2.26
- 4.52

ME-2008-55-mt

Air (at atmospheric pressure) at a dry bulb temperature of 40^{o}C and wet bulb temperature of 20^{o}C is humidified in an air washer operating with continuous water recirculation. The wet bulb depression (i.e., the difference between
the dry and wet bulb temperatures) at the exit is 25% of that at the inlet. The dry bulb temperature at the exit of the air washer is closest to

- 10
^{o}C - 20
^{o}C - 25
^{o}C - 30
^{o}C

ME-2010-42-mt

A moist air sample has dry bulb temperature of 30^{o}C and specific humidity of 11.5 g water vapor per kg dry air. Assume molecular weight of air as 28.93. If the saturation vapor pressure of water at 30^{o}C is 4.24 kPa and the total
pressure is 90 kPa, then the relative humidity (in %) of air sample is

- 50.5
- 38.5
- 56.5
- 68.5

ME-2012-A-31-mt

A room contains 35 kg of dry air and 0.5 kg of water vapor. The total pressure and temperature of air in the room are 100 kPa and 25^{o}C respectively. Given that the saturation pressure for water at 25^{o}C is 3.17 kPa, the relative humidity
of the air in the room is

- 67%
- 55%
- 83%
- 71%

XE-2010-E-16-mt

Air-water vapor mixture having 100% relative humidity at 50^{o}C is heated isobarically to 100^{o}C in a closed system. If saturation pressure at 50^{o}C is 12.352 kPa and at 100^{o}C is 101.42 kPa, final relative humidity
is

- 0%
- 8.2%
- 12.2%
- 100%

Last Modified on: 03-May-2024

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